a) Field of the Invention
The present invention is concerned with an apparatus for measuring a beam width D.sub..sigma.x along a transverse direction of a laser beam. The present invention is also concerned with a method for measuring a beam width D.sub..sigma.x along a transverse direction of a laser beam.
b) Brief Description of the Related Art
Known in the art is U.S. Pat. No. 4,874,939 (Nishimoto et al.), which describes a method and an apparatus for detecting position/variance of input light using linear and quadratic outputs. The apparatus for detecting position/variance of input light includes a photoelectric conversion device receiving input light. The photoelectric conversion device is constituted of a first resistive layer formed of a first photoelectric conversion material and a second resistive layer formed of a second photoelectric conversion material connected with the first resistive layer through a depletion layer or directly. The first resistive layer is provided with uniform resistivity throughout its surface so that a linear output proportional to the average of the distances between one end of the photoelectric conversion device and positions of the input light is detected, and the second resistive layer is provided with resistivity dependent upon the distance from its one end so that a quadratic output proportional to the average of the squares of the distances between one end of the photoelectric conversion device and positions of the input light is detected.
Also known in the art is U.S. Pat. No. 3,809,478 (Talbot), which describes a diffractometer for analyzing the geometrical characteristics of the components of a system. In such a diffractometer the received diffraction pattern is filtered in accordance with a mathematical equation to yield a spatial period spectrum of a moment, excluding the zeroth moment, of that spectrum. The filtering may be effected by means of suitable optical filters for viewing on a screen or for electronic detection, or electronically in the detector circuits.
None of the above described patent shows or describes the necessary means for measuring a beam width D.sub..sigma.x along a transverse direction of a laser beam in a simple manner.